Elephants (Elephas maximus) were brought over to the Andaman Islands for forestry operations, deer(Axis axis, Rusa unicolor, Muntiacusmuntjak, Axis porcinus) for sport hunting, tadpoles of bullfrogs (Hoplobatrachustigerinus) entered the Islands with juvenile fish imported from the mainland as it is often hard to differentiate between the two. Brought as pets to the Islands, cats hunt and destroy populations of indigenous birds elsewhere whereas the Common Myna (Acridotherestristis) once escaped from its cage, has caused havoc to the nests of other birds. These are just a few examples of introduced fauna that have significantly altered the ecosystem by ecological and or economic damage.
Dr. Rauf Ali conducted studies in 2001 and onwards on the introduced species of the Islands. One such study evaluated the impact of elephants (Elephas maximus) at Interview Island in middle Andamans. He found them to have severely damaged the green cover in recent years, causing the regeneration rate to increase abnormally. Damage in the form of uprooted or knocked down trees, or in trees stripped of their bark can be seen firsthand. Another study conducted by him assessed the damage of the introduced spotted deer.He found regeneration to be low in areas where spotted deer (Axis axis) are found, decreasing the basal area and resulting in large areas of the island having sparse vegetation.
Nitya Prakash Mohanty, an independent researcher and alumni of WII, Dehradun, evaluated the impact of introduced spotted deer (Axis axis) on forest floor herpetofauna in the Andaman Islands.Spotted deer, found in North, Middle and South Andamans, browse extensively on seedling and saplings, leading to a potential reduction in the understory vegetation cover. This could have a negative impact on the leaf-eating insects as food availability decreases. The reptiles inhabiting the understory are exposed to predators and to unfavorable conditions. Thus the reduction in overall resources could mean reduction in reptile numbers.